Continuity Tester With Melody

Description :-

 

A continuity tester is a device which tests the continuity of the wire at hand. It is an indispensable tool to check broken wires and undesired shorting of wires.

If we want to check if the wire is connected from one end to another, then use the probes of the continuity tester and put to the ends of the wires to be tested. If the wires are connected, then the circuit makes a sound indicating that the wires is continuous without any break in the middle

CIRCUIT DIAGRAM:



The circuit uses the 555 IC timer in buffer mode. The output of the 555 IC is a DC voltage when the circuit probes detects the connection shorted. This output is given to a music generating IC which is UM66. This music generating integrating circuit is then given the input from the output of the IC 555. The output is high only when the circuit detects the probes are shorted. If not, the output is kept low. The music which is generated by the integrated circuit um66 can he heard through the loudspeaker. The loudspeaker used is a mini 8 ohms loudspeaker. The circuit can be conveniently assembled onto a printed circuit board so that it comes handy whenever we need to test a circuit for continuity or short circuits. A battery power supply can be used for powering this circuit as the circuit is made to consume very little power due to which using a battery based power supply is ideal as the batteries will last longer maintaining the portability of the circuit.

Touch Activated Switch Using CD4011

Description.

A simple touch switch circuit using CD4011 is given here. The IC CD4011 is wires as a flip flop here. The 9, 13 pins of the IC works as the set and reset contacts respectively.CMOS ICs like 4011 require requires a very low current for controlling its gates. Since the pins 9 and 13 are connected to the positive via resistors R1 and R2, the logic gates of the ICs will be in high state. When we touch through the points A, B the gates of the IC will be closed and the output becomes low. This switches ON the transistor Q1 and the relay gets activated. When we touch through the points C, D the gates again becomes high and switches the transistor OFF. This makes the relay OFF. Thus by touching through the contact points A,B and C,D the appliance connected through the relay can be switched On and OFF.

Circuit diagram with Parts list.

Notes.

• The circuit can be assembled on a general purpose PCB.
• The circuit can be powered from 12V DC.
• The IC must be mounted on a holder.
• The relay can be a 12 V, 200 Ohm SPDT relay.

Mobile Phone Incoming Call Detector

Description. 

This circuit can be used to escape from the nuisance of mobile phone rings when you are at home. This circuit will give a visual indication if placed near a mobile phone even if the ringer is deactivated.

When a call is coming to the mobile phone, the transmitter inside it becomes activated. The  frequency of the transmitter is around 900MHz.The  coil L1 picks up these oscillations by induction and feds it to the base of Q1. This makes the transistor Q1 activated.Since the Collector of Q1 is connected to the pin 2 of IC1 (NE555) , the IC1 is triggered to make the LED connected at  its output pin (pin 3) to blink. The blinking of the LED is the indication of incoming call.

Circuit diagram with Parts list. 

 

Notes. 

• The coil L1 can be made by making 150 turns of 36 SWG enameled copper wire on a 5mm dia plastic former.Or you can purchase a 10 uH coil from shop if available.
• The circuit can be powered from a 6V battery.
• Assemble the circuit on a good quality PCB.
• C1 & C3 are to be polyester  capacitors.
• The electrolytic capacitor C2 must be rated 10V.